220 20547 article Path: news.gmane.org!not-for-mail From: =?UTF-8?Q?Tomasz_Kami=C5=84ski?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Draft D0065: Movable initializer lists, rev. 2 Date: Mon, 21 Sep 2015 08:43:37 +0200 Lines: 115 Approved: news@gmane.org Message-ID: References: <87343e65-eecd-4b96-86b7-a883aa7f9d1d@isocpp.org> <6D75256B-F476-4BA4-BA13-D2342F8B7B6B@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=047d7b41889b7d8a1405203c3377 X-Trace: ger.gmane.org 1442817821 26321 80.91.229.3 (21 Sep 2015 06:43:41 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 21 Sep 2015 06:43:41 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDNPVXXG6IGBBGWO72XQKGQE43SW2YI@isocpp.org Mon Sep 21 08:43:40 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vk0-f70.google.com ([209.85.213.70]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Zdup9-0002y8-V7 for gclcip-std-proposals@m.gmane.org; Mon, 21 Sep 2015 08:43:40 +0200 Original-Received: by vkao3 with SMTP id o3sf168619846vka.1 for ; Sun, 20 Sep 2015 23:43:38 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=9g5rEX9nvMUepTymTWw8ds0JIrANH34zDmTKjgW8h7I=; b=gkR0cLrpICLS8ZFyRMjFCdomQ+Gu2QQrpSrK4g2yjplzbkl9lzIrwB+rcIBggZBdo/ JBS+ahJR1QtIk4W8wPaTeQTpAozudStUfbnvsXjLxK2mXLYMxU/KSF7nZCnJIQGnIMAm 0z54GcaoE8q+QLSovXlaTtqCzYkJgZwoGGPy3DSm6ZZCSyjMyaueWWV8/Cw2ZTnjS2J3 ntJfivcfZZvBXjrT8iN1VxxoZ04JjpBDkFK19ooFwazy9ahUSo5PBohErvDOEtJ4n85o SYF5w4sbIB2hpIR/eOeSn1Zw7VVZtRgJ2GpRjbYS2auGnR3HYM1oyeYVXnEKUAzUXdsK +YYA== X-Gm-Message-State: ALoCoQkKRFqNNQoVXL7dgLI5vRini1jc3qgjPeeeVKaPwv1thMWj6WuSrRSVQcli9K7tolB2q1DS X-Received: by 10.140.135.5 with SMTP id 5mr15756473qhh.11.1442817818820; Sun, 20 Sep 2015 23:43:38 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.182.28.99 with SMTP id a3ls835521obh.42.gmail; Sun, 20 Sep 2015 23:43:38 -0700 (PDT) X-Received: by 10.202.192.131 with SMTP id q125mr4259114oif.118.1442817817996; Sun, 20 Sep 2015 23:43:37 -0700 (PDT) Original-Received: from mail-ob0-x232.google.com (mail-ob0-x232.google.com. [2607:f8b0:4003:c01::232]) by mx.google.com with ESMTPS id xe1si11241166oeb.42.2015.09.20.23.43.37 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 20 Sep 2015 23:43:37 -0700 (PDT) Received-SPF: pass (google.com: domain of tomaszkam@gmail.com designates 2607:f8b0:4003:c01::232 as permitted sender) client-ip=2607:f8b0:4003:c01::232; Original-Received: by obbmp4 with SMTP id mp4so40966958obb.3 for ; Sun, 20 Sep 2015 23:43:37 -0700 (PDT) X-Received: by 10.60.81.166 with SMTP id b6mr10177751oey.31.1442817817543; Sun, 20 Sep 2015 23:43:37 -0700 (PDT) Original-Received: by 10.202.87.82 with HTTP; Sun, 20 Sep 2015 23:43:37 -0700 (PDT) In-Reply-To: <6D75256B-F476-4BA4-BA13-D2342F8B7B6B@gmail.com> X-Original-Sender: tomaszkam@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of tomaszkam@gmail.com designates 2607:f8b0:4003:c01::232 as permitted sender) smtp.mailfrom=tomaszkam@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=NONE dis=NONE) header.from=gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:20547 Archived-At: --047d7b41889b7d8a1405203c3377 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 2015-09-21 8:25 GMT+02:00 David Krauss : > > > On 2015=E2=80=9309=E2=80=9321, at 1:41 PM, Tomasz Kami=C5=84ski wrote: > > However, I still think that removing the move-constructor would be > beneficial. The existence of the move-constructor and the name > (own_initializer_list) suggest that the list object actually manages > storage and moves it from one object to another. As the > own_initializer_list is effectively wrapped reference to stack allocated > array, it cannot do that, so the current design is misleading. > > > Does a std::vector (or, as you mention, unique_ptr) =E2=80=9Cmove st= orage > from one object to another=E2=80=9D? Aside from user-replaced ::operator = new or > watching the stack pointer, and aside from the restricted capabilities of > the list, what=E2=80=99s the observable difference between own_initialize= r_list > and unique_ptr? > > The following: std::size_t computeSomething(std::vector); std::function lazyEvaluator() { Type list =3D {"ala", "ola"}; return std::bind(computeSomething, std::move(list)); } Works correctly if Type is std::vector, but if for Type is own_initializer_list it will cause either: 1. dangling reference 2. unreadable warrning about own_initializer_list member in the some strange tuple (I belive that is what your proposal dy). Making own_initializer_list non-movable, will produce error about list being non-moveable. As own_initializer_list is bassically reference, then this is true. --=20 ---=20 You received this message because you are subscribed to the Google Groups "= ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposa= ls/. --047d7b41889b7d8a1405203c3377 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable

= 2015-09-21 8:25 GMT+02:00 David Krauss <potswa@gmail.com>:


On= 2015=E2=80=9309=E2=80=9321, at 1:41 PM, Tomasz Kami=C5=84ski <tomaszkam@gmail.com&g= t; wrote:

However= , I still think that removing the move-constructor would be beneficial. The= existence of the move-constructor and the name (own_initializer_list) sugg= est that the list object actually manages storage and moves it from one obj= ect to another. As the own_initializer_list is effectively wrapped referenc= e to stack allocated array, it cannot do that, so the current design is mis= leading.

Does a std::vector=C2=A0(or, as you mention,=C2=A0unique_ptr<T[]>) =E2=80=9Cmove= storage from one object to another=E2=80=9D? Aside from user-replaced ::operator new or watching the stack pointer, and= aside from the restricted capabilities of the list, what=E2=80=99s the obs= ervable difference between own_initializer_list and unique_ptr<T[]>?


The followin= g:
std::size_t computeSomething(std::vector<std::string>= ;);

std::function<std::size_t()> lazyEva= luator()
{
=C2=A0 =C2=A0Type list =3D {"ala", &q= uot;ola"};
=C2=A0=C2=A0 return std::bind(computeSomethin= g, std::move(list));
}
Works correctly if Type is std::= vector<std::string>, but if for Type is own_initializer_list<std::= string> it will cause either:
1. dangling reference
2. unreadable warrning about own_initializer_list member= in the some strange tuple (I belive that is what your proposal dy).
Making own_initializer_list non-movable, will= produce error about list being non-moveable. As own_initializer_list is ba= ssically reference, then this is true.

--

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